Laser beam measurement of abdominal sagittal diameter in obese children: a validation study.

What is already known about this subject Sagittal diameter (SAD), i.e. the mid height of the abdomen when lying down, has been reported to correlate to visceral fat, insulin resistance and cardiovascular risk factors in adults. SAD seems to be the best anthropometric predictor of cardiovascular risk, and also of more importance than waist circumference (WC) in adults. There has been no validation studies comparing SAD measured with anthropometric tools (e.g. ruler) to measurements made with more exact devices such as magnetic resonance imaging (MRI) in pediatric age. What this study adds This new reliable method is ideal for children due to limited body contact and no radiation. It is accurate, less expensive than MRI, and also easier to perform than measuring WC. It is easily available for screening purposes making future epidemiological studies possible evaluating health risks related to regional distribution of abdominal tissue. OBJECTIVES: Sagittal diameter (SAD) has been reported to correlate to visceral fat and cardiovascular risk factors. SAD is measured with the individual lying down, halfway between the lower rib margin and the iliac crest; it represents the mid-height of the abdomen. The aim of this study was to validate SAD measured using a recently-developed laser beam device (SAD(LDB) ) against SAD measured using MRI (SAD(MRI) ). METHODS: Of 48 obese children (25 boys, 23 girls) aged 9-11 years on the waiting list for obesity treatment, 34 agreed to a baseline measurement, which was followed by repeated measurements 6 and 12 months later in 31 and 22 children respectively. MRI was used to examine SAD(MRI) at 5 cm above (SAD(MRI) (,cra) ) and below (SAD(MRI) (,cau) ) the mid plane of the L4-5 intervertebral disc. RESULTS: Each of the differences SAD(LBD) - SAD(MRI) (,cau) and SAD(LBD) - SAD(MRI) (,cra) was subjected to a repeated-measurements ANOVA; the visit did not have a statistically significant effect in either case (p = 0.19 and p = 0.72, respectively). The difference SAD(LBD) - SAD(MRI) (,cau) was 1.50 on average (p < 0.0001; CI 1.26-1.74) while the corresponding figure for SAD(LBD) - SAD(MRI) (,cra) was 1.26 (p < 0.0001; CI 1.04-1.49). Regression of the difference on the mean gave slopes of -0.09 (p = 0.25) and -0.04 (p = 0.57) respectively. Prediction of SAD(MRI) from SAD(LDB) can be performed in different ways: by means of linear regression or by means of an additive correction. CONCLUSIONS: Thus, this laser device can be used instead of MRI to estimate SAD by using a simple correction.